Study On Nitrification Mechanism Of Ferric Enzyme Activated Sludge Based On The Molecular Biology

Water Eutrophication has attracted the attention from the world since the1970s,especially in the rencnet years, frequent outbreaks of cyanobacteria and red tide had attractedwide attention. The fundamental reason of it lies in the content of nitrogen and phosphorusnutrient substances inwater is exorbitant. Therefore, the fundament way to solve the problemof water eutrophication is controlling nitrogen and phosphorus into water effectively.However, the existing wastewater biological nitrogen and phosphorus removal technology hasthe problems of lower nitrogen and phosphorus removal efficiency, especially the nitrificationin low temperature.The technology of composite ferric enzyme enhanced activated sludge system(CFEECSS) was proposed by Urban Aqua Environmental Pollution Control Research TeamQingdao Technological University. It is throμgh ferric ion getting involved into microbialbiochemical reactions and energy metabolism to improve the activity of metabolic reactionsand then enhance the biological nitrogen and phosphorus removal efficiency; the ferric ioncould improve the structure of activated sludge and then enhance the ability to resist thechange of the external environment factors. The earlier stage of the macro experimentindicates that the CFEECSS not only enhance the biological nitrogen and phosphorus removalefficiency but also enhance the nitrification under lower temperature obviously, and thenimprove the stability of WWTP. However, the micromechanism of it has been littleresearched. So, in the study from two perspectives to research the reason why the CFEASShas the higher nitrification, the first one studied the ammonia-oxidizing bacterial (AOB) andthe nitrite oxidizing bacteria (NOB) community structure of CFEEASS and conventionalactivated sludge system (CASS) at different temperature; the second one studied study theinfluence of ferric ion on the growth and the function gene expression of AOB and NOB.The research results indicated:(1)The removal rate of NH4+-N and the specific nitrification rates of CFEASS is higherthan that of conventional activated sludge system (CASS), and when the iron mass fractionwas5%, the result is the best, then was7%,5%,3%; (2)Ferric ion could improve the stability of AOB and NOB community. We can seenthat in the AOB DGGE atlas the fifth band has been faded and the sixth band emergedgradually, the1~4bands of the NOB DGGE atlas also has been faded with the decreasingtemperature, and the changes became increasingly clear with the system operation throughcontrasting and analyzing the AOB, NOB DGGE atlas of the CFEASS and CASS at differenttemperature However, this phenomenon wasn t obvious in the CFEASS;(3)Ferric ion enhance the diversity of AOB and NOB. We can see from the RFLP atlasof AOB, there were seven species AOB in the CFEASS, while only five species were in theCASS; and thed Maof the CFEASS and CASS was1.03,1.55respectively. The DGGE atlasof NOB showed that the number of NOB in the CFEASS was11~18, while in the CASS wasonly5~13, especially the last sample, the number of NOB is12,7respectively.(4)The ferric ion changed the composition of AOB.It changed the dominant strains ofAOB in the activated sludge. It made the percentage of the bacteria A-2which have a highernitrification capacity increase from40%to67%and the bacteria A-1which have a lowernitrification capacity decrease from40%to23%;(5)The proper concentration of ferric ion could promote the growth of AOB and NOB.When the concerntration of ferric ion is138.7μg/mL,124.8μg/mL respectively, the content ofAOB and NOB is increased by40%,78.5%respectively;(6)Ferric ion could greatly improve the expression of bacterial function gene amoAand NxrA, so make the content of AMO and NXR increase. When the concerntration of ferricion is36.97μg/mL, the relative expression of amoA and NxrA reach the maximum value of5.73and2.48。...